This invention relates to compositions of matter that are useful as catalysts, to a method for preparing the compositions of these catalysts, and to a method of using the compositions as addition polymerization catalysts. More particularly, this invention relates to catalyst compositions, to a method of preparing these catalyst compositions and to a method for polymerizing olefins, diolefins and/or acetylenically unsaturated monomers wherein these catalysts are used.
The use of Ziegler-Natta type catalysts in the polymerization of addition polymerizable monomers is, of course, well known in the prior art. In general, these soluble systems comprise a Group 4 or Lanthanide metal compound and a metal alkyl cocatalyst, particularly an aluminum alkyl cocatalyst.
In U.S. Ser. No. 8,800, filed Jan. 30, 1987, and now abandoned (published in equivalent form as EP 277,004) there are disclosed certain bis(cyclopentadienyl) metal compounds formed by reacting a bis(cyclopentadienyl) metal complex with salts of Bronsted acids containing a non-coordinating compatible anion. The reference discloses the fact that such complexes are usefully employed as catalysts in the polymerization of olefins. For the teachings contained therein the aforementioned U.S. Ser. No. 8,800 (now abandoned) and EP 277,004 are herein incorporated in their entirety by reference thereto.
Disadvantageously it has now been found that catalysts prepared according to the foregoing technique are detrimentally affected by the presence of by-product amine compounds resulting from the catalyst formation. That is, the procedure of EP 277,004 involves an irreversible reaction between a ligand of the metal compound and a cation of the Bronsted acid salt. In practice such cations are generally trialkyl ammonium ions that result in the formation of a tertiary amine by proton transfer to the ligand during catalyst formation. Such amine compounds are undesirable components of the resulting catalyst due to their inhibiting effect on addition polymerizations.
It would be desirable if there were provided a addition polymerization catalyst that is activated in a manner that forms only noninterfering and inert byproducts.
In J. Am. Ch. Soc. 109, 4111-4113 (1987) there is disclosed a process for preparation of cationic zirconium (IV) benzyl complexes by one electron oxidation of d.degree. organometallic compounds. The solvents employed in the preparation of the zirconium metallocenes were tetrahydrofuran or methylene chloride both of which interfere with the desired catalyst formation and or detrimentally affect subsequent olefin polymerizations. In addition the reference employed an oxidizing agent containing tetraphenylborate. Such anions, it has now been discovered, are unacceptable for use in an oxidation activation process for preparing addition polymerization catalysts.
It has now been discovered that the foregoing and other disadvantages of the prior art ionic olefin polymerization catalysts can be avoided or at least reduced with the catalysts of the present invention. In addition an improved catalyst activation procedure and improved addition polymerization processes are provided according to the present invention. It is, therefore, an object of this invention to provide improved ionic catalyst systems which are useful in the polymerization of addition polymerizable monomers including olefins, diolefins and/or acetylenically unsaturated monomers. It is another object of this invention to provide a method for preparing such improved catalysts. It is a further object of this invention to provide an improved polymerization process using such improved catalysts. It is still another object of this invention to provide such an improved catalyst which is not subject to formation of interfering compounds. Finally it is an object of this invention to provide such an improved catalyst which may permit better control of the product polymer molecular weight and molecular weight distribution.